<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="renderer" content="webkit">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>数据类型</title>
</head>
<body>
    <input id="username" type="text" placeholder="请输入用户名">
    <div>
        <p>
            <a href="#"></a>
            <img src="" alt="">
            <span></span>
        </p>
        <h2></h2>
        <div></div>
    </div>
</body>
<script>
    // var i = document.getElementById("username");
    // i.value.trim();

    var a = 4;
    function b(){
        a = 3;
        a = function(){
            
        }
        console.log(a);
    }
    b();

   /*  var a = 4 ;
    console.log(typeof a);
    console.log(a instanceof Number);

    var a =2;
    var b = 4;
    console.log(b)
    console.log(window.b);

    function demo(){
        var c = 123;
    }
    demo(); */


  /*   var xm = {
        name:'小明',
        age:18,
        gender:'男',
        study:function(){
            console.log("学习");
        }
    }

    var num = 6<<4;
 */
   /*  for (const key in xm) {
        if (xm.hasOwnProperty(key)) {
            console.log(key);
            const element = xm[key];
            console.log(element)
            
        }
       
    } */

   /*  for (const key in undefined) {
        console.log(key);
    } */

    /* function demo(){
        if(a){
            if(b){
                if(c){

                }
            }
        }else if(b){

        }else if(c){

        }else if(c){
            
        }else if(c){
            
        }else if(c){
            
        }else if(c){
            
        }else if(c){
            
        }else{}


        return new Date();
    }

    var abc =demo();
    console.log(abc); */

    /* try {
        
    } catch (error) {
        
    }finally{

    } */

  /*   function a(){
        console.log("aaa")
    } */

  /*   function bb(){
        console.log("bbb")
        bb();
    }

    bb(); */


 /*  var c =   function(a){
      console.log(this);
      console.log(a)
      console.log("cc");
  } 

//   console.log(typeof c);
  var a= c.apply("hello");
  console.log(a); */

 /*  function demo(a,b,c){
    console.log(arguments[1])
  }

  demo(1,2,3); */

  /* function Person (name , age){
      this.name = name;
      this.age = age;
      this.show=function(){
          console.log(this.name,this.age);
      }
  }

    $("div.demo > p").live("click",function(){

    })  */ 
    // 以文件协议打开文件  
    // file:///E:/CodeDemo/18%E7%BA%A7%E5%89%8D%E7%AB%AF%E8%AF%BE%E7%A8%8B/web2jQueryCode/%E5%A4%8D%E4%B9%A0/01%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B.html
    // http://127.0.0.1:5501/%E5%A4%8D%E4%B9%A0/01%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B.html


    var a= 10;

    function demo (arg1){
        // 代码块
        console.log(arg1);
    }


    demo();

    function demo2(){
        demo();
        // 
    }

    demo2();

</script>

</html>